1. Field of the Invention
The present invention relates to an image forming apparatus having mounted thereon a power supply device arranged between an external power supply and an electric power load and capable of storing electric power.
2. Description of the Related Art
Conventionally, electronic equipment, such as an electrophotographic image forming apparatus, has a so-called low-power consumption mode in which, when the device has not been used for a certain period even with a main power supply turned on, supply of electric power is temporarily stopped except for a portion of a circuit, such as a control system circuit, to achieve energy saving.
Such electronic equipment has a power supply circuit generating a DC power supply to be supplied to the control system circuit from a commercial AC power supply. Supply of electric power to the control system circuit and the like for which supply of electric power is continued even in the low-power consumption mode is performed by that power supply circuit.
However, the DC power supply supplied from such a power supply circuit in the low-power consumption mode is a high output of about 80% of rated power, for example. It is a portion of the control system circuit for which supply of electric power should actually be continued even in the low-power consumption mode, and about 30% of rated power of the DC power supply at most is required. Therefore, maintaining a high output of about 80% of rated power in the low-power consumption mode will be wasteful from the viewpoint of energy saving, and further energy saving needs to be achieved.
Therefore, Japanese Patent No. 4336318, for example, proposes a system in which a charging unit serving as an auxiliary power supply is provided, and electric power stored in that charging unit is used in the low-power consumption mode, thereby achieving further energy saving.
However, if electric power stored in the charging unit is not enough, a commercial power supply needs to be used.